Filing your self-assessment tax return might sound intimidating if you’re not an accountant. But if you’re self-employed, a freelancer, a landlord, or earn income outside of PAYE, it’s something you’ll likely need to do. The good news? You can file your self-assessment tax return without an accountant – and with a little organisation and the right information, it’s easier than you might think.
In this guide, we’ll walk you through how to file a self-assessment tax return online in the UK without professional help. You’ll learn about registration, essential documents, calculating tax-deductible expenses, key deadlines, and tips to avoid common mistakes.
What Is a Self-Assessment Tax Return?
A Self-Assessment tax return is a system used by HMRC to collect Income Tax from individuals whose earnings aren’t taxed automatically. This includes income from self-employment, rental properties, dividends, or other sources.
Who Needs to File One?
You must file a self-assessment return if you:
- Are self-employed or a sole trader earning over £1,000
- Receive income from property rentals
- Have foreign income
- Earn £100,000+ annually
- Receive dividends or savings income not taxed at source
Check HMRC’s eligibility page for a complete list.
Step-by-Step Guide to Filing a Self-Assessment Tax Return Without an Accountant
1. Register with HMRC
If this is your first time filing, you must register for self-assessment with HMRC. Do this by 5 October following the end of the tax year in which you earned untaxed income.
You’ll need:
- Your National Insurance Number
- Personal details (address, date of birth)
- Business information if self-employed
Once registered, HMRC will send you a Unique Taxpayer Reference (UTR) number and instructions for setting up your Government Gateway account.
2. Collect Necessary Information
Here’s a tax return checklist for the UK:
- Your 10-digit UTR number
- National Insurance Number
- Details of income (employment, self-employment, rental, savings, dividends, etc.)
- P60/P45 (if employed)
- Records of allowable tax-deductible expenses
- Pension contributions, charitable donations
- Details of student loan repayments (if applicable)
- Bank interest or investment income
Staying organised throughout the year makes this step much easier.
3. Calculate Income and Expenses
Income
Include all income sources, such as:
- Business income (if self-employed)
- Rental income
- Dividends and investments
- Foreign income
Expenses
You can deduct legitimate tax-deductible expenses like:
- Office supplies
- Business travel
- Phone and internet
- Use of home for business
- Accounting software
Use HMRC’s simplified expenses calculator if applicable.
4. Log in and Fill Out Your Return Online
Once you have your UTR and Gateway account, go to HMRC’s Self Assessment Portal and:
- Log in with your Government Gateway ID
- Select “Start your tax return”
- Follow each section step-by-step
- Enter income details and allowable expenses
- Complete the summary and check for errors
HMRC automatically calculates the tax you owe based on the information you provide.
5. Review and Submit
Before clicking “submit”, double-check your entries. A small mistake can lead to penalties or overpayment. Once submitted, save the confirmation email and tax calculation for your records.
You can also pay your tax bill through:
- Direct Debit
- Bank transfer
- Debit/credit card
- HMRC’s Budget Payment Plan
Key Deadlines You Must Know
| Action | Deadline |
| Register for self-assessment | 5 October |
| Paper tax return | 31 October |
| Online tax return | 31 January |
| Pay tax bill | 31 January |
Missing these deadlines can lead to fines starting at £100, plus interest.
Tips to File Without an Accountant
Use Accounting Software
Free and paid tools like FreeAgent, QuickBooks, or Xero help track income and expenses efficiently.
Keep Digital Records
Maintain digital or cloud-based receipts and records. HMRC’s Making Tax Digital initiative may soon require this.
Learn from HMRC Resources
HMRC offers free webinars and help sheets that explain complex topics in simple language.
Double Check Your UTR and NI
Ensure these are accurate as errors can delay processing.
Submit Early
Filing early not only avoids stress but also gives you more time to budget for any tax you owe.
Common Mistakes to Avoid
- Not registering on time
- Forgetting to include all income
- Claiming ineligible expenses
- Missing the deadline
- Failing to keep records for 5 years
If you realise you’ve made a mistake after submitting, don’t panic. You can amend your return online within 12 months of the filing deadline.
Why File It Yourself?
While accountants provide value, filing your return yourself:
- Saves money on fees
- Increases financial literacy
- Gives you more control over your business
- Helps you understand how much tax you owe and why
Plus, with tools like HMRC’s portal and online calculators, it’s more accessible than ever.
When Should You Still Consult an Accountant?
Filing it yourself is fine for straightforward cases, but consult an accountant if:
- You have complex income (foreign earnings, trusts, etc.)
- You’re unsure about capital gains
- You’re facing an HMRC investigation
- You’ve missed previous deadlines and want to mitigate penalties
Final Thoughts
Filing your self-assessment tax return without an accountant is entirely possible – and increasingly common in the UK. With proper preparation, digital tools, and a clear understanding of what HMRC requires, you can confidently manage your tax affairs on your own.
If you’re looking for a fast, affordable, and secure way to file online, visit Quick Tax Returns UK – a reliable self-assessment filing service for freelancers, landlords, and business owners.
FAQs
1. Can I file a self-assessment tax return for free?
Yes, you can file for free directly through HMRC’s website if you don’t require advanced features.
2. Do I need a UTR number to file online?
Absolutely. It’s a 10-digit unique code that HMRC uses to identify you.
3. What happens if I miss the 31 January deadline?
You’ll face an automatic £100 penalty, with more added the longer you delay.
4. Is online filing safe?
Yes. HMRC uses encrypted portals, and by using secure browsers and devices, you can keep your data safe.
5. Can I change my return after submitting it?
Yes, within 12 months of the deadline.